Implantable cardiac stimulation and sensing devices are well known in the art. Such stimulation devices may include, for example, pacemakers or defibrillators. These devices are generally implanted in an upper portion of the chest beneath the skin of a patient within a surgically-created subcutaneous pocket.
Screw-in leads are notoriously costly and complex and have a lot of variation in performance. These characteristics are built into the lead because of the desire to shield the veins and tricuspid valve from the fixation helix during lead insertion. Many mechanisms have been employed for extending and retracting the helix, including a screwdriver-tipped stylet and a rotatable inner conductor attached to the helix. Because of the complexity of these various mechanisms, the leads that employ them are costly, complex, and subject to variable performance.
Currently-used active fixation transvenous cardiac leads are designed to utilize one of the following types of fixation approaches along with their recognized drawbacks:                1. “exposed fixed” helix; during insertion, the exposed fixed helix can be traumatic to vasculature and the tricuspid valve;        2. “fixed helix with a protective coating” wherein the exposed helix is coated with a dissolving substance, e.g. mannitol or polyethylene glycol (PEG); when the protective substance is dissolved, a fixed exposed helix, remains. Unfortunately, if the coating dissolves prematurely or if the lead needs to be removed and reinserted, the resulting lead continues to exhibit the same issues as No. 1 above;        3. the “rotating pin” extendable-retractrable helix which is retracted within the lead's distal housing until the helix is intended to be extended and fixated (that is, screwed) into the heart tissue. With this type of helix, the connector pin is rotated to rotate the conductor coil to rotate and extend the helix out of the lead's tip and screw it into the tissue. A major advantage of this helix extension/retraction approach is that it can be relatively easily positioned at almost any site in the right atrium (RA) and right ventricle (RV). A major disadvantage of this approach is that a large diameter, stiff protective header is used to house the helix during lead insertion, which causes the lead to be stiffer and larger diameter and/or the helix to be smaller diameter than would otherwise be optimal.        4. The “screwdriver stylet” extendable-retractable helix system is configured such that the wire stylet has a screwdriver tip at its distal end that engages into a slot at the proximal base of the helix electrode, and which then is used to screw the helix out in a one-to-one rotating ratio which is a very positive benefit; however, this design requires stocking specialized stylets.        
It was in light of the foregoing known apparatus and techniques that the present invention was conceived and has now been reduced to practice.